Used by some building societies to uniquely identify an individual’s account (usually a savings account). Sometimes referred to as an Account Number (not to be confused with a Bank Account Number) or a customer reference number. In this situation, the building society will use one or more head-office collection accounts from another bank. For onward submission to Bacs, the Roll Number has to appear in the reference field in the Bacs file (alpha-numeric, up to 18 characters).
Please also see Bank Account Validation - Bank Wizard and Bank Account Validation